1. Field of the Invention
The present invention relates to a tape library having a plurality of cells containing tapes which can be accessed at any time for reading and writing data, and more particularly to an accessor device for accessing such tapes.
2. Description of the Related Art
FIG. 1 of the accompanying drawings shows a conventional tape library 51 comprising a plurality of joined housings. In FIG. 1, the tape library 51 is viewed from above with an inner mechanism being made visible. In the tape library 51, the housings 53, 56 house therein respective linearly symmetrical accessor devices 54, 57 each having a hand mechanism 55 for accessing mediums (tapes). The accessor devices 54, 57 are movable along a single guide rail 58 disposed centrally in the tape library 51 for accessing cells 52 containing mediums and a drive (not shown).
The accessor device 54 has an accessor base 54-10 in the shape of a rectangular parallelepiped, and has two rollers 54-21, 54-22 mounted on a side surface thereof and spaced from each other by a pitch i.
The accessor device 57 has an accessor base 57-10 in the shape of a rectangular parallelepiped that is in a linearly symmetrical relationship to the accessor device 54, and has two rollers 57-21, 57-22 mounted on a side surface thereof and spaced from each other by a pitch j.
The two accessor devices 54, 57 are movable bidirectionally on the guide rail 58.
In FIG. 1, the accessor devices 54, 57 are shown as retracted and stopped in the respective housings 53, 56. Cells 52-1, 52-2 are endmost cells 52 that can be accessed by the hand mechanisms 55 of the accessor devices 54, 57.
When one of the accessor devices 54, 57 suffers trouble and is unable to access the cells, operation of the tape library 51 is controlled in the same manner as with the present invention.
It is assumed that the accessor device 57 suffers trouble and is retracted and stopped. Due to the trouble, the accessor device 57 is unstable to access the cells 52 or the non-illustrated drive, and is stopped in a retracted area in the housing 56.
At this time, the other accessor device 54 moves a distance k, is spaced a distance m from the retracted and stopped accessor device 57, and accesses the cell 52-2, and completes its operation.
The conventional tape library 51 has had the following problems:
The first problem is that it is difficult to prevent the accessor devices 54, 57 from falling in the direction in which they move.
The reason for the first problem is that since the two accessor devices 54, 57 move on the single guide rail 58 with the two rollers 54-21, 54-22 (57-21, 57-22), the pitch or distance between the two rollers 54-21, 54-22 (57-21, 57-22) cannot be increased.
The second problem is that the number of cells 52 accessible by both the two accessor devices 54, 57 is small.
The reason for the second problem is that because the accessor bases 54-10, 57-10 of the accessor devices 54, 57 are in the shape of a rectangular parallelepiped and are mounted in a linearly symmetrical relationship to each other, the accessor bases 54-10, 57-10 cannot be brought closely to each other as they fail to overlap each other when moved toward each other.
It is therefore an object of the present invention to provide an accessor device which is prevented from falling and can access an increased area in a tape library.
To accomplish the above object, there is provided in accordance with the present invention an accessor device for a tape library having a plurality of cells housing mediums and two guide rails extending parallel to each other along the cells, comprising two accessor bases mounted for movement along the guide rails, and two hand mechanisms mounted respectively on the accessor bases for accessing the mediums, the accessor bases having on confronting portions thereof respective overlapping edges which can overlap each other in a direction normal to the longitudinal direction of the guide rails.
Each of the accessor bases may has a pair of first rollers held in rolling engagement with one of the guide rails, and a second roller held in rolling engagement with the other of the guide rails.
Each of the accessor bases may be substantially of a triangular shaving having a first side extending along the guide rails, a second side having an end joined to an end of the first side substantially perpendicularly to the first side, and a third side interconnecting other ends of the first and second sides, the overlapping edges comprising the respective third sides confronting each other when the accessor bases overlap each other in the direction normal to the longitudinal direction of the guide rails.
Each of the accessor bases may has a pair of first rollers mounted on the first side respective at opposite ends thereof, and a second roller disposed at a junction between the second side and the third side.
Each of the hand mechanisms may be mounted on the second side of one of the accessor bases.
The third side of each of the accessor bases may be of a crank shape.
Each of the accessor bases may has an actuating mechanism for moving each of the accessor bases, the actuating mechanism being mounted on the second side.
Each of the accessor bases may has a lifting and lowering mechanism for lifting and lowering each of the hand mechanisms, the lifting and lowering mechanism being mounted on the second side.
The accessor device according to the present invention offers two major advantages as follows:
According to the first advantage, while each of the accessor bases is of a relatively large size, the number of cells that can be accessed alternately by the two accessor bases is increased.
The reason for the first advantage is that the overlapping edge of each of the accessor bases is defined as if cut from an accessor base blank, and when the accessor bases move toward each other, the accessor bases overlap each other in the direction normal to the longitudinal direction of the guide rails. The accessor bases create an overlapping region, and hence can efficiently utilize a space for being positionable closely to each other.
According to the second advantage, the accessor device is prevented from falling.
The reason for the second advantage is that the accessor bases are mounted on the two guide rails. Two rollers, which are spaced from each other by a large pitch, on each of the accessor bases are mounted on one of the guide rails to prevent the accessor device from falling along the guide rails, and one roller on each of the accessor bases is mounted on the other guide rail to prevent the accessor device from falling across the guide rails.
The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate an example of the present invention.